This invention relates to surgical instruments for thermally-mediated treatments of tissue, and more particularly relates to a system for shrinking, sealing, welding or creating lesions in tissue by means of injection of a thermal energy laden vapor media into a body structure wherein the vapor-to-liquid phase change of the media applies energy to the tissue.
Various types of radiofrequency (Rf) and laser surgical instruments have been developed for delivering thermal energy to tissue, for example to cause hemostasis, to weld tissue or to cause a thermoplastic remodeling of tissue. While such prior art forms of energy delivery work well for some applications, Rf and laser energy typically cannot cause highly “controlled” and “localized” thermal effects that are desirable in microsurgeries or other precision surgeries. In general, the non-linear or non-uniform characteristics of tissue affect both laser and Rf energy distributions in tissue. The objective of sealing or welding tissue requires means for elevating the tissue temperature uniformly throughout a targeted site.
What is needed is an instrument and technique (i) that can controllably deliver thermal energy to non-uniform tissue volumes; (i) that can shrink, seal, weld or create lesions in selected tissue volumes without desiccation or charring of adjacent tissues; (iii); and (iv) that does not cause stray electrical current flow in tissue.